play how you need to win now...
learn skills that make you a complete player so that if you lose pace, you'll still have touch shots, court positioning and a good tennis brain.
loopy topspin takes as much effort as hitting through the ball.. both will be difficult when you are 60+.
answer, play as you are but add:
- drop shot and lob.
- ability to play at the net (volley, drop volley, playing doubles etc..)
- a decent backhand slice will go a long way
- understand directionals and other tennis strategies.
Disclaimer: I'm NOT a coach...
Real tennis: https://www.youtube.com/watch?v=yDqnkLJ9BtM